Different operation tools for performing technical operations downhole, e.g. tools for milling and filtering, are known. These operations may take place in horizontal or vertical wells, or a deviation between the two.
A device for removing sand using the coiled tubing technique is known from U.S. Pat. No. 5,447,200. The device disclosed in this patent is used for removing high viscosity materials, such as sand and fluid mixed up with sand and other solid elements in a fluid. The sand or high viscosity fluid mixed with sand is pumped from the well to the surface in order to clean the sand out of the well. This is a very energy-consuming process. Furthermore, the device and method described in the patent are not suitable for combining with a filter unit in order to separate solids from liquids, as the device is only constructed for pumping the entire substance to the surface.